Stiller said doctors dealt him a real shock in June 2014 when they told him he was sick, and that he hadn't even had a urologist two weeks before experts delivered the bad news.

"It came out of the blue for me. I had no idea," Stiller said. "At first, I didn't know what was gonna happen. I was scared. It just stopped everything in your life because you can't plan for a movie because you don't know what's gonna happen."

Thankfully for Stiller, surgery and treatments were successful, and he was free of cancer only three months after his diagnosis.

Stiller added he and doctors ultimately determined his tumor had been growing over the course of five years, and credits the prostate-specific antigen test with saving his life. Now, he's encouraging men to be extremely vigilant about PSA testing, and shared an additional essay outlining his experience via Medium.

"If [the doctor] had waited, as the American Cancer Society recommends, until I was 50, I would not have known I had a growing tumor until two years after I got treated," Stiller wrote. "If he had followed the U.S. Preventive Services Task Force guidelines, I would have never gotten tested at all, and not have known I had cancer until it was way too late to treat successfully."